A lot harder than plaster of paris. Use for making casts which need to be hard wearing. The proportions of new stone powder to water should be 100 powder to 28 water by weight. e.g. 3.5kgs powder to 1 litre water. Add the powder to the water gently and mix well. The consistency will be thick and creamy. The initial setting time is 18 minutes. Wait until the casting has cooled before de-moulding.